The Screening Myth
Breast-cancer screening has long been viewed as one of the most important tools for reducing mortality from the disease. But the 25-year follow-up of the Canadian National Breast Screening Study, published in February, tells a very different story.
TORONTO – Breast-cancer screening has long been viewed as one of the most important tools for reducing mortality from the disease. That is why recent doubts about its effectiveness – intensified by the publication in February of the 25-year follow-up to the Canadian National Breast Screening Study – have come as such a shock. How can breast-cancer screening, which facilitates early detection of the disease, not prevent deaths from it?
Understanding screening’s limitations requires, first and foremost, an understanding of the process. A mammogram (x-ray of the breast) is administered to ostensibly healthy people to detect unsuspected disease. If any abnormalities are found, a diagnostic test is conducted to confirm the presence of the disease. If the results are positive, treatment begins.
The first limitation of breast-cancer screening is obvious: where effective diagnosis and treatment are not available, screening cannot have any impact. But there is more to the issue – namely, whether screening ultimately fulfills its intended purpose of reducing breast-cancer mortality rates.
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